Association between Short -Term Exposure to Air Pollution and COVID-19 Mortality: A Population -Based Case -Crossover Study Using Individual -Level Mortality Registry Confirmed by Medical Examiners

BACKGROUND: Studies have suggested links between ambient air pollution and coronavirus 2019 (COV ID-19) mortality, yet confirmation by welldesigned epidemiological studies with individual data is needed. OBJECTIVES: We aimed to examine whether short-term exposure to air pollution is associated with risk of mortality from COVID-19 for those infected with COVED -19. METHODS: The Cook County Medical Examiner's Office reports individual -level data for deaths from COVID-19 that occur in its jurisdiction, which includes all confirmed COVID-19 deaths in Cook County, Illinois. Case -crossover analysis was conducted to estimate the associations of estimated short-term exposures to particulate matter (PM) with aerodynamic diameter <= 2.5 tm (P1M(2.5)) and ozone (03) on the day of death and up to 21 d before death at location of death with COVID-19. A total of 7,462 deaths from COVID-19 that occurred up to 28 February 2021 were included in the final analysis. We adjusted for potential confounders by time -stratified case -crossover design and by covariate adjustments (i.e., time -invariant factors, meteorological factors, viral transmission, seasonality, and time trend). RESULTS: Of the 7,462 case and 25,457 self-control days, almost all were days with exposure levels below the PM2,5 24-h National Ambient Air Quality Standard (NAAQS) (35 vg/ m3); 98.9% had 03 levels below the maximum 8-h NAAQS (35.7 p.g/m(3) or 70 parts per billion). An interquartile range (IQR) increase (5.2)tg/m(3)) in cumulative 3 -wk PM2.5 exposure was associated with a 69.6% [95% confidence interval (CI): 34.6, 113.8] increase in risk of COVID-19 mortality. An IQR increase (8.2)tg/m(3)) in 3-d 03 exposure was associated with a 29.0% (95% CI: 9.9, 51.5) increase in risk of COVID-19 mortality. The associations differed by demographics or race/ethnicity. There was indication of modification of the associations by some comorbid conditions. DISCUSSION: Short-term exposure to air pollution below the NAAQS may increase the mortality burden from COVED-19.

Automated summary

Short-term exposure to air pollution, specifically PM2.5 and ozone, is associated with an increased risk of mortality from COVID-19. An increase in PM2.5 exposure over three weeks is linked to a 69.6% higher risk, while a three-day exposure to ozone is associated with a 29.0% higher risk. There are variations in these associations among different demographics and racial/ethnic groups.